To protect security of data, and for an objective of disaster recovery, storage vendors establish a remote disaster recovery center to implement remote data backup, so as to ensure that original data is not lost or damaged after a disaster (such as a fire and an earthquake) occurs, and to ensure that a key service resumes within an allowed time range, thereby reducing a loss caused by the disaster as much as possible.
Current disaster recovery systems mainly include: a 2 center disaster recovery system and a 3 data center (3DC) disaster recovery system. In the 2 center disaster recovery system, disaster recovery is implemented by establishing two data centers, where an active data center is used to undertake a service of a user, and a standby data center is used to back up data, a configuration, a service, and the like of the active data center. When a disaster occurs in the active data center, the standby data center may take over the service of the active data center. In the 3DC disaster recovery system, disaster recovery is implemented by using storage systems deployed at the three data centers. Generally, in the 3DC disaster recovery system, the three data centers may be respectively referred to as a production site, a level-1 site, and a level-2 site. Generally, the level-1 site and the level-2 site are disaster recovery sites, the production site and the level-1 site may be located in two different locations in a same city, and the level-2 site and the production site are located in different cities. In an existing 3DC disaster recovery system, disaster recovery is generally implemented among the three data centers by using a synchronous remote replication technology and an asynchronous remote replication technology. Because reliability and scalability of the 3DC disaster recovery system are relatively good, a scope of application of the 3DC disaster recovery system is wider.
However, in the existing 3DC redundancy system, when data needs to be replicated to a level-2 site, generally, a production site or a level-1 site replicates the data to the level-2 site; therefore, data replication efficiency is not high.